The present invention relates to a power transmission device, particularly a power transmission device that includes a belt-type continuously variable transmission.
Conventionally, a type of power transmission device has been known that includes a belt-type continuously variable transmission that has a primary pulley that is provided on a primary shaft, a secondary pulley that is provided on a secondary shaft, and a belt that is passed around both of the pulleys (for example, refer to Japanese Patent Application Publication No. JP-A-2002-181175). In the power transmission device, a primary hydraulic actuator (a hydraulic cylinder) is used to vary a groove width of the primary pulley, and a secondary hydraulic actuator (a hydraulic cylinder) is used to vary a groove width of the secondary pulley, such that power that is transmitted from an engine to the primary shaft through a forward/reverse switching mechanism can be continuously varied and output to the secondary pulley. The power transmission device also has a manual valve that is capable of selectively supplying to a forward clutch and a reverse clutch of the forward/reverse switching mechanism a working fluid that is supplied from a clutch modulator valve at a pressure that is roughly equal to a line pressure. That is, when a D range for driving forward is selected as a shift range, the working fluid is supplied from the clutch modulator valve, through the manual valve, to a hydraulic servo of the forward clutch, and when an R range for driving in reverse is selected as the shift range, the working fluid is supplied from the clutch modulator valve, through the manual valve, to a hydraulic servo of the reverse clutch.